Anti-human immunodeficiency virus hematopoietic progenitor cell-delivered ribozyme in a phase I study: myeloid and lymphoid reconstitution in human immunodeficiency virus type-1-infected patients.

A phase I gene transfer clinical study was undertaken to examine the ability to introduce a potential anti-human immunodeficiency virus (HIV) gene therapeutic into hematopoietic progenitor cells (HPC), thereby contributing to multilineage engraftment. The potential therapeutic effect of genetically modifying HPC with protective genes in HIV-infected adults depends in part on the presence of adult thymic activity and myeloid capacity in the setting of HIV replication. Herein we report the presence and expression of a retroviral vector encoding an anti-HIV-1 ribozyme in mature hematopoietic cells of different lineages, and de novo T-lymphocyte development ensuing from genetically engineered CD34(+) HPC. Sustained output of vector-containing mature myeloid and T-lymphoid cells was detected even in patients with multidrug-resistant infection. In addition, the study showed that the degree of persistence of gene-containing cells was dependent on transduced HPC dose. These novel findings support the concept of gene therapy as a modality to effect immune reconstitution with cells engineered to inhibit HIV replication and this report represents the first demonstration of long-term maintenance of a potential therapeutic transgene in HIV disease.

Clinical gene therapy research utilizing ribozymes: application to the treatment of HIV/AIDS.

Antiretroviral drug therapy can effectively reduce the viral load, and is associated with a degree of immune reconstitution in human immunodeficiency virus (HIV)-infected patients. However, the presence of a latent viral reservoir, the development of drug resistance, drug toxicity, and compliance problems are obstacles that impede full eradication of HIV through drug therapy. The cellular introduction of genetic elements that are capable of inhibiting HIV replication is conceptually appealing as a potential new treatment paradigm for acquired immunodeficiency syndrome (AIDS). In theory, this approach can lead to the development of regenerated hematopoiesis with cells that inhibit viral replication and are protected from the pathogenic effects of HIV. Ribozymes are catalytic RNA molecules that can efficiently and selectively cleave target RNA. By ex vivo retroviral transduction, we have introduced a HIV-1 tat gene-targeted ribozyme (RRz2) and a control construct (LNL6) into granulocyte-colony-stimulating factor (G-CSF) mobilized CD34+ hematopoietic progenitor cells (HPC). Transduced autologous CD34+ cells (an approximately equal mix of RRz2 and LNL6) were infused in 10 patients in this Phase I study. After a median follow-up of 2.5 yr, gene presence and expression were detected by a sensitive polymerase chain reaction (PCR) assay in a transduced-CD34+ cell dose-dependent manner. In this chapter, we describe general considerations related to HIV hematopoietic progenitor-cell gene therapy trial design, implementation, and safety, with an emphasis on the critical steps of this process, namely vector production and characterization, target-cell selection, transduction, final product release testing, and evaluation of vector presence.

Critical steps in the implementation of hematopoietic progenitor-cell gene therapy using ribozyme vectors: a laboratory protocol.

The implementation of a hematopoietic progenitor-cell gene-therapy program involves the performance of laboratory procedures and compliance with the current code of Good Manufacturing Practices. This chapter explains the multiple laboratory steps used in our recent Phase I gene transfer study for HIV. This study employed a retroviral vector to deliver an anti-HIV ribozyme to CD34+ hematopoietic progenitor cells.